What operators do NOT exist in EK9?

defines module qa.aimistakes.invalidoperators

  defines function

    <?-
      Shows correct alternatives to operators that don't exist.
    -?>
    classify() as pure
      -> score as Integer
      <-
        rtn as String: String()

      rtn := switch score
        <- grade as String: String()
        case >= 90
          grade: "excellent"
        case >= 70
          grade: "good"
        case >= 50
          grade: "pass"
        default
          grade: "fail"

    <?-
      Shows correct list access — no [] operator in EK9.
      Use get() method, not [] indexing.
    -?>
    getItemCount() as pure
      -> items as List of String
      <- rtn as Integer: length items

    <?-
      Shows correct approach instead of safe navigation (?.)
      Use guard expression instead.
    -?>
    safeLength() as pure
      -> text as String
      <- rtn as Integer: 0

      if text?
        rtn := length text

  defines program

    CorrectOperatorsDemo()
      stdout <- Stdout()

      // Switch expression — NOT ternary
      grade <- classify(85)
      stdout.println(`Grade: ${grade}`)

      // Method call — NOT [] indexing
      names <- ["Alice", "Bob", "Charlie"]
      nameCount <- getItemCount(names)
      stdout.println(`Names: ${nameCount}`)

      // Guard expression — NOT ?. safe navigation
      textLength <- safeLength("hello")
      stdout.println(`Length: ${textLength}`)

      emptyLength <- safeLength(String())
      stdout.println(`Empty length: ${emptyLength}`)

      // Postfix ++ only — NOT prefix ++
      counter <- 0
      counter++
      counter++
      stdout.println(`Counter: ${counter}`)